Cerebral oximetry is an optical method that measures cerebral tissue oxygen saturation (SctO2) continuously and non-invasively at the bedside. Complimentary to pulse oximetry, which only measures arterial oxygen saturation (SaO2), cerebral oximetry measures parameters that mostly reflect regional metabolism and the balance of local tissue oxygen supply/demand. Therefore, an accurate cerebral oximeter would have a wide range of applications, both in basic research and clinical settings. However, current cerebral oximeters have yet to achieve their initially expected potential of becoming a routine clinical monitor like pulse oximeters. The main challenge for clinical application of cerebral oximeters has been to demonstrate the effectiveness of such monitors. The critical issue that needs to be addressed is the development of algorithms that are able to quantify the optical signals and therefore derive absolute values of SctO2. More importantly, it is necessary to establish threshold StO2 values that correlate with patients'clinical outcomes for various clinical situations. In Phase II validation study of our proof-of-concept prototype cerebral oximeter, we demonstrated that our empirically derived novel algorithm could determine absolute cerebral SctO2 with a high degree of accuracy in the adult human. We hypothesize that our commercial absolute cerebral oximeter will perform similarly for adult humans. The proposed studies will focus on transforming the existing proof-of-concept prototype cerebral oximeter into a commercial product. Furthermore, we will conduct validation and clinical outcome studies to demonstrate the effectiveness of our commercial cerebral oximeter. If successful, we will commercialize the first FDA approved absolute cerebral oximeter, since commercial cerebral oximeters currently approved by the FDA are for trending only monitoring. In addition, we anticipate that result from the proposed clinical outcome studies will provide physicians guidance to establish threshold SctO2 values for various clinical situations.